Cellular communications systems typically include multiple base stations for communicating with mobile stations in various geographical transmission areas. Each base station provides an interface between the mobile station and a telecommunications network. Mobile telephone systems are in use or being developed in which the geographic coverage area of the system is divided into smaller separate cells, it communicates with the network via a fixed station located in the cell. Mobile telephones belonging to the system are free to travel from one cell to another. When a subscriber within the same system or within an external system wishes to call a mobile subscriber within this system, the network must have information on the actual location of the mobile telephone.
Recently, the price of cellular telephone has been greatly reduced and become affordable to lots of people. It is common that a person owns more than one cellular phone. Some people even replace their cellular telephones as often as they replace their clothes or hairstyle. The cellular manufactures have to release new models with different appearances, function and styles more frequently so as to attract the attention of the buyer and occupy a favorable marketing share. Furthermore, the conventional projector employ white light lamp as a light source, therefore, at least two reflector lens and at least three light-split lens are required to split the white light into three colors (red, green and blue). The optical lens set is expensive. The mechanism of the optical system is too complicated and the size can not be reduced. Further, the lamp source will generate heat with high temperature. Another type projector is called digital light projector, U.S. Pat. Nos. 6,733,137, 6,988,808 disclose such projector. The type of projector employs DMD (digital micro-mirror device) and a color wheel for projecting. The digital mirror device has several hundreds of thousand of mirror elements and it is capable of reducing a difference in chromaticness (tint) caused by performance/characteristic variation between filters or between light sources. A driving unit controls an inclination of each of mirror elements of a DMD panel according to a corrected video signal and a revolution state of a color filter wheel and wherein the correcting unit corrects luminance signal for each color of video signals by calculating a relative intensity of light having passed through each filter making up the color filter wheel using the output of a photosensor occurring when each mirror element of the DMD panel is put in the OFF state. The color filter wheel is driven by a motor and it's size is not small, consequently, it is unlikely to embedded the projecting device into a portable device. Further, the conventional technical employs white light as the light source and it generates high temperature heat during operation. The projector needs a lot of lens to cooperate with the light source and the color filter wheel as well. Low-frequency flashing effect will occurs due to the white light passing through the high speed revolution color wheel which is driven by the motor. As recognized herein, for portability, it is desirable to configure the projector to be as slim as possible. But the goal of size reduction is frustrated by the present of the elements mentioned above.